The present invention relates in general to pedestrian protection systems in automotive vehicles, and, more specifically, to including rigid structures such as accessories on a vehicle instrument panel within a pedestrian protection zone while maintaining low impact forces to a pedestrian during an impact.
An important objective in the design of motor vehicles is to provide structural properties that limit the potential for injuries to pedestrians (e.g., walkers and cyclists) that may result from collisions with a vehicle. One important criteria for evaluating pedestrian impacts relates to the magnitude of impact forces generated when the head of a pedestrian impacts at various areas of the vehicle (referred to as a pedestrian protection zone). This zone may include the vehicle's hood over the engine compartment (i.e., bonnet) and the windshield. The zone corresponding to the windshield may require consideration of structures beneath the windshield such as a cowl and an instrument panel.
Voluntary guidelines and governmental regulations have specified target impact performance in terms of a head injury criteria (HIC) or a head performance criteria (HPC) at specified points in the pedestrian protection zone at the forward end of the vehicle. The target may be based upon the magnitude of acceleration experienced and the time over which it occurs as an estimate of the potential severity of injury. The potential for injury is proportional to the stiffness of vehicle structures coinciding with the protection zone. A structure with a lower stiffness that crumples (i.e., yields) more readily in response to an impactor creates a lower risk of injury than a structure with a higher stiffness since the higher stiffness generates a higher impact force against the impactor.
A typical pedestrian protection zone includes at least a forward portion of the windshield and structures beneath the windshield, which may typically include a forward edge of the instrument panel that is mounted within the passenger cabin. Historically, the forward edge of the instrument panel has tended to be relatively soft and has been lacking in stiff structures that caused issues for maintaining low impact forces. More recently, however, it has become desirable to relocate certain instrument panel components to a position on the instrument panel that is more forward. This relocation may be motivated by a desire to provide additional storage space within the instrument panel or to shrink the overall size of the instrument panel. Accessory components which may be moved into the protection zone include a passenger airbag module, a heads-up display, an audio speaker, and a defrost vent, for example. Consequently, respective portions of the instrument panel within the pedestrian protection zone may become stiffer, resulting in concerns about meeting pedestrian protection objectives.
Externally mounted air bag systems can be deployed to provide protection in the area of the windshield during a pedestrian impact. However, such systems are complex and expensive. A supplemental internal air bag system is generally not feasible because of the limited space available within the instrument panel and between the surface of the instrument panel and the windshield. It would be desirable to introduce “hard points” on an instrument panel within a pedestrian protection zone while maintaining pedestrian protection without requiring air bags.